Fix building OBS Studio on FreeBSD

[obiwac]

Description

Fix building OBS Studio on FreeBSD:

• libobs/graphics/graphics.h: The gs_texture_create_from_dmabuf & gs_query_dmabuf_* functions were marked as Linux-only as of f7a55f4.
• plugins/linux-v4l2/v4l2-output.c: versionsort (and by extension, __strverscmp) are not available on FreeBSD, as they are GNU extensions (versionsort is used by virtualcam_start to read /dev/video* devices in the right order), so implemented them.
• UI/platform-x11.cpp: Was calling to_string on FreeBSD when not using namespace std;, so calling std::to_string instead.

Motivation and Context

Fixes building on FreeBSD.

How Has This Been Tested?

Tested on FreeBSD 13.0-RELEASE-p4 and FreeBSD-CURRENT, hardware is non-applicable.
Compiled with clang version 11.0.1 & 13.0.1.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

Perhaps this is usererror, but git-clang-format doesn't seem to work?

YAML:35:21: error: unknown key 'AfterExternBlock'
  AfterExternBlock: false
                    ^~~~~
Error reading /usr/home/obiwac/obs-studio/.clang-format: Invalid argument
error: `clang-format -lines=178:178 -lines=187:187 -lines=191:191 -lines=196:196 -lines=198:255 -lines=258:258 -lines=260:260 plugins/linux-v4l2/v4l2-output.c` failed

So I attempted to format things myself.
Hope that's alright :)

[kkartaltepe]

I don't think we will want to include an implementation of versionsort from glibc just for freebsd. Is there an alternative function that can be used on freebsd?

[obiwac]

I don't think we will want to include an implementation of versionsort from glibc just for freebsd. Is there an alternative function that can be used on freebsd?

Yeah, it's not ideal indeed, but again, to my knowledge and after a good look, I don't think there is.
There does exist alphasort though, as can be seen in the scandir(3) manual, but that means differing behaviour on different platforms.

Also, alphasort is not a good solution as it would order devices as follows:

/dev/video0
/dev/video1
/dev/video10
/dev/video2
...
/dev/video9

I guess I could implement a bit of a simpler sorting function without considering the fractional part for both Linux & FreeBSD?

[kkartaltepe]

Also, alphasort is not a good solution as it would order devices as follows:

It seems a decent solution to enable building on freebsd without introducing a large amount of platform specific code. You could consider leaving the results unsorted on freebsd as well perhaps the devices will simply be in the proper order for most users.

[WizardCM]

From CI:

clang-format-12 is /usr/bin/clang-format-12
=================================
Files were not formatted properly
plugins/linux-v4l2/v4l2-output.c

[obiwac]

You could consider leaving the results unsorted on freebsd as well perhaps the devices will simply be in the proper order for most users.

Can confirm this is not the case, unfortunately :(

Something like this could always be used:

static int devsort(const struct dirent **_a, const struct dirent **_b) {
	int a = atoi((*_a)->d_name + 5);
	int b = atoi((*_b)->d_name + 5);

	return a - b;
}

This would eliminate the need for any platform specific code whatsoever, as it works both on Linux & FreeBSD. (Strings aren't sorted if not numeric.)

From CI:

clang-format-12 is /usr/bin/clang-format-12
=================================
Files were not formatted properly
plugins/linux-v4l2/v4l2-output.c

That's my bad, still figuring out how to use this clang-format stuff.

[obiwac]

Implemented that function I mentioned in my previous comment. Is it better like that or should I just choose between alphasort on FreeBSD and versionsort on Linux?

[kkartaltepe]

I would prefer a function that wont do bad things in case it gets odd input, and it seems the only one available for BSD users with libc is alphasort.

Though I suspect no one will sort before filtering in their scandir implementation but if they did, us reading invalid memory is not a good idea.

[obiwac]

Sure, I was operating under that assumption initially, and from that point of view I don't think anything bad could happen.

Regardless, I'll replace it with a simple alphasort/versionsort depending on platform in a bit.

[obiwac]

Done

[kkartaltepe]

Please squash away the obsoleted commits, after that it seems good to merge.

[obiwac]

Yup, of course

[obiwac]

There we go!

[kkartaltepe]

You squashed the to_string fix into the v4l2 fix if you could split that back out or make note in the commit desc.

[obiwac]

There we go.